A large mass of material retains a lot of heat in the middle of the part, and the edges cool faster than the middle. This differential of cooling causes the edges to pull up off of the build sheet because there isn’t enough holding power to hold the part down flat to the build sheet.
Orient your STL file and slice it as you normally would.
Before generating Supports, open the Support Parameters dialog (from the Main Menu, select Support > Setup, then click on the Access Advanced Support Settings icon) and increase the Base Oversize setting (figure 1). This parameter can be set at up to .500”, and will provide a larger base area to bond to the build sheet. As a result, when the part is being built and the large base layers of the part are shrinking, there will be more area contacting the build sheet to hold it flat.
Another way to achieve this, if an even larger base is desired, is to use the Offset command. Once you have generated the standard supports and base, select Edit > Offset from the main menu (figure 2).
a. Make sure the “Offset Direction” box is set to Outside Closed Curve.
b. Enter a measurement in the “Offset Distance” field.
c. Make sure the “Destination Group” is set to Same as Selected.
d. Important: Select No in the “Keep Original” field! Otherwise, the
offset curves will form a new inner / outer relationship with the existing base curves, and no base will be created under the part!
e. Select all the light blue (base) and dark blue (base top) curves at the bottom of the part and click OK. A new larger base has now been created.
For more information, download the full best practices document here.